In the following, a zinc die-cast housing for a plug connector for establishing an electrical connection between the plug and a socket receiving said plug will be described, as well as a corresponding manufacturing method for it and the casting mould on which the housing is based.
Such plug connectors are, in particular, employed in the field of industrial control and feedback control systems and serve, for example, to connect larger electronic equipment such as, e.g., computers or industrial robots with power supplies or other electrical components.
The housing of the plug connector is usually composed of two housing parts in which insulating body inserts equipped with contact elements are respectively provided, whose contact elements come into contact when coupling the housing parts. The housing parts are kept together by means of a locking device which engages with attachment elements which are provided both on the first and the second housing part to be joined.
The purpose of the housing itself is to protect the insulating body inserts which are accommodated therein against external mechanical and electromagnetic influences. To this end, housing parts made from metal or synthetic material known in the art are manufactured which have a sufficient mechanical strength to prevent damage to the elements accommodated therein due to external effects. The housing parts may be provided with an electro-conductive coating on their surfaces, which allows an electrical connection between the two housing parts and thereby ensures an adequate protection against electromagnetic interfering influences from the outside for the contact means in the housing interior. Likewise, an electromagnetic interference radiation which occurs in the housing interior cannot escape to the outside.
Further, an elastic sealing ring may be provided for a housing of such plug connectors, which is arranged between the two housing parts in order to protect the housing interior against the ingression of dirt and humidity. In this case, however, care should be taken that the elastic sealing does not interrupt the electro-conductive connection between the housing parts. Such plug connector housings are known, e.g. from DE 92 18 209 U1, DE 43 39 210 C1, or EP 0 957 540 A2.
Practical operation, however, has also revealed several drawbacks with respect to the manufacture of the described housings according to the state of the art. These housings are presently often manufactured by means of a corresponding tool to the pressure die casting method. The material of primary choice is aluminium or aluminium alloys, respectively. Due to the relatively low electrical conductivity of aluminium and aluminium alloys, it is necessary to provide the aluminium housing parts manufactured by the die cast method in a further step with a surface coating with a better conductivity in order to enable an electrical shielding of the plug connector.
Additionally required elements such as fastening elements for mounting the locking device by means of which the two housing parts are kept together, or a receptacle device for receiving and applying electrical contact to a cable to be connected with the plug connector are subsequently installed in the housing parts, e.g., by pressing or screwing them into pre-formed holes.
In order to ensure a good and continuous electrical connection of the two housing parts, it is often required as recommended in DE 43 39 210 C1, to finish-machine the surface of the housing parts at least in the region of the contact areas by, e.g., face grinding.
Due to the fact that the die-cast aluminium housing parts have to be finish-machined in several steps, and that multiple additional single parts are required for making a housing, which have to be assembled with the housing parts within an assembling process, additional storage costs as well as assembly and manufacturing costs will accrue.
Another known disadvantage in conjunction with the aluminium die casting method or the die casting method with aluminium cast alloys, respectively, is that the maximum shot number with one tool set, i.e. the number of castings which can be manufactured with one tool set of the necessary tools for die casting, such as mould, piston, etc., is limited to approx. 100.000 pieces for plug connectors. This, in turn, results in increased manufacturing costs because with higher unit numbers the expensive tools, in particular, the high-price mould, have to be replaced.